<template>
    <div>
        <router-link tag="div" to="/" class="header-abs" v-show="showAbs">
            <div class="iconfont header-abs-back">&#xe625;</div>
        </router-link>   
        <div class="header-fixed" v-show="!showAbs" :style="opacityStyle">
            <router-link to="/">
                <div class="iconfont header-fixed-back">&#xe625;</div>
            </router-link>
            景点详情
        </div>    
    </div>
</template>

<script>
    export default {
        name : "Header",
        data () {
            return {
                showAbs: true,
                opacityStyle: {
                    opacity: 0
                }
            }
        },
        methods : {
            handleScroll(){
                //document.documentElement.scrollTop   pc端使用  document.body.scrollTop 移动端使用
                console.log(document.documentElement.scrollTop)
                const top = document.body.scrollTop || document.documentElement.scrollTop
                if (top > 60) {
                    let opacity = top / 140
                    opacity = opacity > 1 ? 1 : opacity
                    this.opacityStyle = { opacity }
                    this.showAbs = false
                } else {
                    this.showAbs = true
                }
            },
        },
        activated() { 
            window.addEventListener('scroll',this.handleScroll)
        },
        deactivated() { //页面即将替换新的页面的时候
            window.removeEventListener('scroll',this.handleScroll)
        }

    }
</script>

<style lang="stylus" scoped>
@import '~styles/varibles.styl'
    .header-abs
        position: fixed
        left: .2rem
        top: .2rem
        width: .8rem
        height: .8rem
        line-height: .8rem    
        border-radius: .4rem
        text-align: center
        background: rgba(0, 0, 0, .8)
        .header-abs-back
            color: #fff
            font-size: .4rem
        
    .header-fixed
        position: fixed
        top : 0
        left : 0 
        right : 0
        z-index : 2
        height: $headerHeight
        line-height: $headerHeight
        text-align: center
        color: #fff
        background: $bgColor
        font-size: .32rem
        .header-fixed-back
            position: absolute
            top: 0
            left: 0
            width: .64rem
            text-align: center
            font-size: .4rem
            color: #fff
</style>